[FFmpeg-devel] [PATCH] avcodec/h264_slice: don't copy frame data during error concealment

[James Almer]

In addition to the fact that av_image_copy() cannot handle hardware pixel
formats, h->short_ref[0]->f may not even be writable at this point.

Based on a patch by Hendrik Leppkes.

Signed-off-by: James Almer <jamrial at gmail.com>
---
This is an alternative to "avcodec/h264_slice: properly handle missing
reference frames with hwaccel", given that I noticed that the target frame is
not writable for example when running fate-h264-missing-frame.

To keep the current behavior of copying the frame data instead of making a
reference, I also tried to do ff_thread_release_buffer() ->
ff_thread_get_buffer() -> av_frame_copy(), which worked with software decoding,
but when using the d3d11va hwaccel the av_frame_copy() call would fail.

There is a warning above this code that makes it sound like making references
is not ideal, but considering h->short_ref[0] is not writable here it feels
like it could be an outdated comment that someone forgot to remove.

 libavcodec/h264_slice.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/libavcodec/h264_slice.c b/libavcodec/h264_slice.c
index fa7a639053..a2f4ffa6d6 100644
--- a/libavcodec/h264_slice.c
+++ b/libavcodec/h264_slice.c
@@ -1599,13 +1599,11 @@ static int h264_field_start(H264Context *h, const H264SliceContext *sl,
                 ff_thread_await_progress(&prev->tf, INT_MAX, 0);
                 if (prev->field_picture)
                     ff_thread_await_progress(&prev->tf, INT_MAX, 1);
-                av_image_copy(h->short_ref[0]->f->data,
-                              h->short_ref[0]->f->linesize,
-                              (const uint8_t **)prev->f->data,
-                              prev->f->linesize,
-                              prev->f->format,
-                              prev->f->width,
-                              prev->f->height);
+                ff_thread_release_buffer(h->avctx, &h->short_ref[0]->tf);
+                h->short_ref[0]->tf.f = h->short_ref[0]->f;
+                ret = ff_thread_ref_frame(&h->short_ref[0]->tf, &prev->tf);
+                if (ret < 0)
+                    return ret;
                 h->short_ref[0]->poc = prev->poc + 2U;
             } else if (!h->frame_recovered && !h->avctx->hwaccel)
                 ff_color_frame(h->short_ref[0]->f, c);
-- 
2.30.1